Historically, instrument gauges used in the instrument clusters of cars and trucks have been designed for a single mode of operation. For example, a tachometer that displays engine speed is designed to provide a very fast gauge pointer response for closely following changes in engine speed. On the other hand, a fuel gauge that displays the level of fuel in the fuel tank is designed to provide a very slow gauge pointer response so that the driver does not see the results of fuel slosh when the vehicle accelerates, decelerates, or makes a turn. This historical approach has been proven over time to appear very satisfactory from the view point of the driver; however, when all factors bearing on the total information conveying system are concerned, it is believed that certain beneficial improvements can be made that will assure continued driver satisfaction while offering new economies and versatilities in the manufacture, fabrication, and servicing of instrument gauge systems, particularly systems that employ instrument gauges having electromechanical movements, like air core gauges, and that also employ modern electronics that interface the gauges to the various signal sources, like speed sensors, pressure sensors, levels sensors, communication data links, etc.
Although air core gauges have enjoyed wide usage for many, many years, they continue to enjoy significant usage in the age of electronics because they provide certain advantages that newer electronic readouts have not yet been able to achieve. Perhaps, most significant of these advantages are cost, durability, and ease of reading.
An air core gauge can be fabricated in a cost-effective manner. Once an air core gauge has been installed and found to be operating properly, it should provide reliable service for the life of the vehicle in normal circumstances. Because an air core gauge uses a pointer to indicate its reading, the driver can quickly see if a reading is normal or abnormal.
An electronic gauge that comprises a digital readout is generally more costly, and the value of the parameter which it displays may require interpretation by the driver in order to determine if the reading is normal or abnormal. While the latter attribute of a digital electronic readout may not always be true in the case of a digital speedometer, a digital tachometer, or a digital fuel level gauge, it is often true in the case of other readouts.
In a known instrumentation system in which electromechanical gauges interface with their signal sources via microprocessor-based electronics, a common procedure in finalizing a functional system comprises programming the signal source, the calibration data, and the mode of operation for each gauge by means of an electronic programming tool.
Insofar as the applicant is aware, it has heretofore not been proposed to utilize the programming tool to also program into the electronics a desired response characteristic that defines how fast or slowly the electromechanical gauge movement is to respond to a given change in the signal from the associated signal source.
The present invention relates to an improvement whereby the programming tool is utilized to also program such a desired response characteristic into the electronics for each gauge. This improvement can provide important benefits in the manufacture, fabrication, and servicing of instrumentation systems having gauges with electromechanical movements.
One advantage of the invention is that there can be a greater commonality of gauges because the response speed of the movement of a particular gauge is established by programmed data, and not by the particular physical construction of the gauge. Heretofore, a common practice for establishing the speed of response of a gauge has been to choose a particular viscosity for a dampening fluid, i.e. a dampening oil, introduced into the gauge during the process of making it. Thus, a gauge for a particular application was heretofore often unique to that application because of the particular response speed best suited for the operating parameter being displayed on the gauge. This meant that in a typical instrument cluster, a number of unique gauges would be required. For example, because a gauge that is suited for tachometer use requiring fast response would be inherently poorly suited for fuel gauge use requiring slow response, and vice versa, unique gauges would be required for each.
With the present invention, such diverse uses can nevertheless employ common gauges in an instrument cluster, since the speed at which the gauge is to respond (i.e. gauge speed response) is, in each instance, programmed into the electronics by the electronic programming tool contemporaneously with programming of the associated signal source (i.e. sensor or data link) and the requisite calibration (i.e. matching the span of the gauge movement to the range of the signal from the source) for the gauge being programmed.
By thus increasing the commonality of gauge usage, fewer unique gauges are required, and this offers the potential for economies of scale, since a larger number of common gauges can be produced, and the number of unique gauges can be reduced. This simplifies inventory and parts requirements as well.
The ability to electronically program the gauge response offers still further advantages. If a vehicle operator wishes a given gauge to have a different response speed, i.e. if the response is deemed either too fast or too slow, the electronics need only be re-programmed by the programming tool with a different response speed. Thus, any particular gauge can be expeditiously customized for an operator either before or after the operator takes delivery of the vehicle.
Testing of an instrument cluster can also be more quickly accomplished with the present invention. For example, the movement of a fuel gauge which typically has a slow response speed can be tested as if it had a fast response speed either by by-passing the programmed slow speed response at time of testing or by temporarily substituting a fast speed response for the slower one during the test.
Implementation of the invention may be considered as programming a particular "weight" of a software filter that is configured in the microprocessor-based electronics as part of the processing of a raw data signal by which the raw signal is converted to a form suitable for output to a gauge drive circuit that drives the corresponding gauge movement. Such "weighted" software filtering is independent of any signal calibration that is required to be performed by the microprocessor-based electronics to match the span of the signal to the span of the gauge. Thus, although a preferred implementation of the invention may possess software aspects, the invention is physically embodied in hardware, albeit hardware that has been programmed from an external source.